The lunar surface-exosphere connection: Measurement of secondary-ions from Apollo soils

Radiation Effects on Airless Bodies in Space: Radiolysis, Sputtering, and Sintering in Regoliths

“…Material can also leave the surface as molecular species as has been shown most dramatically in ice for which, H 2 O, O 2 and H 2 can be the dominant ejecta [Brown and Johnson, 1986]. Similarly, SiO, Si 2 , SiO 2 , and Si 2 O are all sputter products from SiO 2 , and similar molecules were seen in the ion spectra of lunar soils and simulants [Schaible, 2014;Dukes and Baragiola, 2015;Elphic et al, 1991].…”

“…The ejected ions can be directly analyzed using an IMS, thereby allowing detection of reactive metal ions and molecules which would otherwise stick to the instrument walls before they could be ionized and measured. It has long been suggested that secondary ions could be used to determine the composition of airless bodies in space [Johnson and Baragiola, 1991;Dukes and Baragiola, 2015;Johnson and Sittler, 1990], and recent spacecraft have shown promise by obtaining rough elemental analyses of both atmospheres [Waite et al, 2004;Fox, 2015] and surfaces [Mahaffy et al, 2014;Balsiger et al, 2007] using this technique. This work combines laboratory data and simulations to estimate the material ejection rates and the resulting neutral and ion fluxes as a function of altitude above a small body on which sputtering is occurring.…”

“…Experimental data for sputtering of oxides and minerals of relevance to planetary and asteroidal bodies with ∼ keV H + and He + at solar wind energies is sparse. However, measurements of the ejected ion spectra due to solar wind ion bombardment have been carried out on a small number of returned lunar soils [Schaible, 2014;Dukes and Baragiola, 2015] and soil simulants [Elphic et al, 1991;. These studies found that the sputtered ion composition for lunar soils can be correlated to the bulk composition using an ionization energy dependent relative yield.…”

“…Surface compositional changes have been identified through X-ray photoelectron spectroscopy (XPS) measurements of sputter-induced surface compositional changes in minerals due to solar wind type ion irradiation. For example, the composition of San Carlos olivine in the uppermost several nm (the depth of sensitivity for the XPS technique) was seen to undergo a depletion in the atomic fraction of oxygen at the surface and the formation of elemental Fe [Pieters et al, 1993;Dukes et al, 1999;Loeffler et al, 2009;Dukes and Baragiola, 2015]. Specifically, metallic iron is enriched at the surface of Fe containing silicates bombarded with 4 keV He + ions and has been suggested to account for reddening of silicates such as the lunar soil [Hapke, 1965[Hapke, , 2001Pieters et al, 1993].…”

“…Additionally, the optical imaging system (OIS) will be used to determine the libration amplitude to determine internal structure, as well as to analyze PADME NIMS-E instrument were in the ion detection mode since neutral refractories quickly stick to the detector walls and, due to low volatility, require either very high partial pressures or long dwell times in order to be detected. It has long been suggested that secondary ions could be used to determine the composition of airless bodies in space [Johnson and Sittler, 1990;Johnson and Baragiola, 1991;Dukes and Baragiola, 2015]. Recent spacecraft have shown the promise of obtaining detailed elemental analysis of ions from both atmospheres such as those of Titan [Waite et al, 2004] and Mars [Fox, 2015] and from airless surfaces such as the Moon [Mahaffy et al, 2014] and comets [Balsiger et al, 2007].…”